Since Watergate, presidents and their aides have warned that impeachment is destabilizing to foreign policy. But history suggests otherwise. Presidential scandals create uncertainty abroad, but the impeachment process itself seems to bring clarity and resolution.

Keep this lesson in mind this week as the Senate begins its trial of President Trump. The president’s advocates will argue (as he himself has already) that impeachment and trial are harmful to America’s image abroad and derail normal foreign policy. But the evidence doesn’t support that dire view.

Foreign adversaries, to be sure, are opportunists. They take advantage of divisions and discord in the United States. As former secretary of state Henry Kissinger wrote, “A great power is given no quarter because it has trouble at home.” But the constitutional mechanism of impeachment is accepted abroad as part of America’s constitutional architecture of stability, even in divided times.

The impeachment bookshelf is a good reality check as you watch the Senate trial and wonder about its impact on foreign policy. A good start are the memoirs written by the two modern presidents who were threatened by impeachment, Richard M. Nixon and Bill Clinton, and by their secretaries of state. They convey the trauma of investigation but also the benefit of formal closure — through resignation in Nixon’s case and acquittal in Clinton’s.

Nixon wrote a note of foreboding in his diary on New Year’s Day 1974, as the Watergate scandal was deepening: “Fight because resignation could lead to a collapse of our foreign policy initiatives.” But as he recounted in his 1978 memoir, “RN,” the momentum of foreign policy continued, thanks in part to Kissinger, who operated almost as a prime minister for overseas policy. Before Nixon resigned in August 1974, he and Kissinger could celebrate an Israel-Egyptian disengagement agreement in Sinai that was a prelude to an eventual peace deal and a summit with the Soviet Union that laid groundwork for another arms-control agreement.

Kissinger, Nixon wrote, “had the effrontery to show the nation and the world that the United States under my leadership was still able to command respect in the world and achieve significant results despite the drag of Watergate.”

In his memoir “Years of Upheaval,” Kissinger agonized about the “tornado of suspicion,” “weakening authority” and his fear of “stagnation in our foreign policy.” But the fundamental trends affecting the Middle East, the Soviet Union and China were already set. He described how his “theatrical” diplomacy showed that “America could survive its anguish and still build a better world.”

Among Nixon’s last reveries, shortly before his resignation on Aug. 8, 1974, was imagining what leaders would be thinking in Moscow, Beijing and other capitals he had visited. But by then, it was probably mostly relief that the Watergate roller coaster was ending.

Clinton, too, feared the disruptive foreign policy effects of the impeachment process through 1998 and into 1999. Though we remember 1998 as a relatively calm time, the year included al-Qaeda terrorist attacks on U.S. Embassies in Africa, and U.S. retaliatory attacks; bombing of suspected chemical and biological weapons sites in Iraq; intensive Israeli-Palestinian diplomacy; wars in Africa; a North Korean missile test; and the aftermath of an Asian financial crisis.

Clinton complained in “My Life” that a cynical media treated his military actions as “a real-life version of ‘Wag the Dog,’ a movie in which a fictional president starts a made-for-TV war to distract public attention from his personal problems.” (Trump has faced the same half-baked criticism.) Clinton was popular abroad, and he writes that “having the support of world leaders . . . helped to keep my spirits up.”

Madeleine Albright, Clinton’s secretary of state during the Monica Lewinsky scandal and subsequent impeachment, remembers that, like Kissinger, she was determined “to steer a steady course” in foreign policy. It helped, she wrote in “Madam Secretary,” that “my colleagues from around the world couldn’t understand why anyone would care what the president might or might not have done.”

A consistent theme through the Nixon and Clinton dramas, and now with Trump, is the presidents’ conviction that they didn’t commit any impeachable offenses and that the process is a partisan political sham.

Nixon wrote: “I never for a moment believed that any of the charges against me were legally impeachable.” Clinton declared in his memoir that his impeachment was “a politically motivated action by a majority party in Congress that couldn’t restrain itself.”

And so it goes. Impeachment is an inherently political process for resolving allegations of abuse of power, as the Founders intended. But past evidence suggests that it helps break the fever, rather than making it worse.

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